Recently, there is a growing interest in the automatic analysis of learner activity in web-based learning environments. The approach and system SIAM (System for Interaction Analysis by Machine learning) presented in this article aims at helping to establish a basis for the automatic analysis of interaction data by developing a data logging and analysis system based on a standard database server and standard machine learning techniques. The contribution is the integration of components which are appropriate for large amount of data. The analysis system has been connected to the web-based interactive learning environment for mathematics, ActiveMath, but is designed to allow for interfacing to other web-based learning environments, too. The results of several usages of this action analysis tool are presented and discussed. They indicate potentials for further development and usages. (Contains 3 tables and 5 figures.)